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Identifying Celestial Bodies

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Celestial Bodies?

Or Celestial Bodies?

Exploring the Universe

Mars Pathfinder rover Sojourner with the rock “Yogi”

Samples Collected from Mars

Scientists use a dichotomous key to identify things, by splitting a group into two groups based on a difference in a particular characteristic. Each group is then divided into two more groups based on another characteristic. This continues until only one organism is left and this leads the scientist to the name of the object being identified.

Key to the Critters on Mars

Identify this Martian!

Antares

Antares gleams with a red light in the heart of the constellation of Scorpius. It is often mistaken for the red planet, a fact shown by its name, Antares, which means “Like Mars” in Greek. Unlike Mars, Antares produces its own light. In fact, it is 10,000x more luminous than the Sun and has a radius 883x that of the Sun. If Antares were placed in the center of our solar system, its outer surface would lie between the orbits of Mars and Jupiter. A trip to visit Antares would take 550 light-years but if you got up just before dawn this morning (January 19, 2012), you could have see Antares light up the southeast sky near the waning crescent moon.

Antares

Eagle

Eagle receives its name for the overall shape of the cloud of hydrogen gas and interstellar dust that forms it. It produces a diffuse emission of light. Eagle is a region of active current star formation that is about 6,500 light-years distant. Within the cloud, the columns and pillars of gas and dust act as incubators for new stars. Dark areas in the pillar structures are believed to be protostars.

Pillars within Eagle where stars are forming.

Eagle

Orion

Orion is one of the most recognizable patterns of stars in the northern sky. In mythology, Orion was a hunter, armed with bow and arrows. His life ended tragically when he stepped on Scorpius, the scorpion. The gods felt sorry for Orion and put him in the night sky, but on the opposite side of the sky from Scorpius, so he couldn’t be harmed again. From the northern hemisphere, the three bright stars in a straight line that form Orion’s Belt are easily visible on the southern horizon in winter evenings. The bright star that forms Orion’s left shoulder is Betelguese. The name of this star means “The armpit of the Central One” in Arabic, which shows that this pattern of stars was recognized across many cultures.

Orion

Andromeda

Andromeda is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. Andromeda is disk-shaped with dusty, curving arms. It is visible to the naked eye on moonless nights even when viewed in areas with moderate light pollution. Astronomers expect Andromeda to collide with the Milky Way in 4.5 billion years. NASA has used X-ray technology to image the bulge in the center of Andromeda. X-ray emission measurements indicate that a supernova explosion caused by a normal star falling onto a white dwarf star is occurring there.

Andromeda

Saturn

Saturn orbits the sun between Jupiter and Uranus. We see Saturn because it reflects light from the Sun. Saturn’s interior is probably composed of a core of iron, nickel and rock, surrounded by a deep layer of metallic hydrogen and liquid helium and an outer gaseous layer. Saturn has a radius that is 9x that of Earth, but has only 1/8th the average density of Earth because so much of the planet is composed of gas. Saturn has a ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit Saturn. Titan, Saturn’s largest moon, is larger than the planet Mercury.

Saturn

Size comparison between Saturn and Earth

Pluto

Pluto is the tenth-most-massive body observed directly orbiting the Sun. We can see Pluto with telescopes because it reflects light from the Sun. It is one of several large bodies within the newly charter Kuiper belt. Pluto shares its orbital neighborhood with Kuiper belt objects, such as plutinos. These bodies are of comparable size to Pluto but are not in its gravitational influence. Like the other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately 1/5th the mass of the Earth’s Moon and 1/3rd of its volume. Pluto has an eccentric and highly inclined orbit that causes it to periodically come closer to the Sun than Neptune.

Pluto

Pluto is one of several large bodies orbiting the Sun in the Kuiper Belt, shown in green.

Io

Io orbits the planet Jupiter as a natural satellite. Io does not produce its own light, but reflects light from the Sun. With over 400 active volcanoes, Io is the most geologically active object in the solar system. This extreme geologic activity is the result of the tidal heating from friction generated within Io’s interior as it is pulled between Jupiter and the other Galilean satellites – Europa, Ganymede, and Callisto. Unlike most satellites in the outer Solar System, which are mostly composed of water ice, Io is primarily composed of silicate rock surrounding a molten core of iron or iron sulfide. Although most of Io’s surface is extensive plains coated with sulfur dioxide frost, is also has more than 100 mountains, some of which are taller than Earth’s Mount Everest.

Io

Io shown orbiting Jupiter

Io

Vesta

Vesta is one of several irregularly shaped bodies that orbits the Sun in a belt between the planets Mars and Jupiter. It has a mean diameter of about 530 km and together with Ceres, Pallas, and Hygieacontains half the mass of the entire belt. It does not produce its own light, but reflects light from the Sun. Vesta has an enormous crater 460 km in diameter centered near its south pole. It also has three adjacent craters that look like a snowman. Vesta is thought to consist of a metallic iron-nickel core, an overlying rocky olivine mantle, with a surface crust. Some of the small Solar System bodies are believed to be fragments of Vesta caused by collisions.

Vesta

Vesta

Earth’s Moon

Hale-Bopp

Hale-Bopp is an icy small Solar System body that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the Hale-Bopp and not because produces its own light. Hale-Bopp was visible to the naked eye for a record of 18 months starting in May of 1996. Hale-Bopp displayed two tails, a blue gas tail pointing straight away from the Sun and a yellowish dust tail curving away along its orbit. Hale-Bopp has a long orbital period, prior to 1996, it’s last visit to Earth was in July 2215 BC. Because of it’s long elliptical orbit, Hale-Bopp can take approx. 3000-4000 years to orbit around the Sun.

Hale-Bopp

The Great Daylight 1972 Fireball

The Great Daylight 1972 Fireball passed within 57 km of the surface of the Earth on August 10, 1972. It entered Earth’s atmosphere in daylight over Utah, United States and passed northwards leaving the atmosphere over Alberta, Canada. The Fireball did not produce its own light or heat like a star. At a distance, it reflected light from the Sun, eventually burning up as it experienced friction with the Earth’s atmosphere. Analysis of its appearance and trajectory showed that it would have been 3 m in diameter, if made of carbonaceous chondrite, to 14 m, if made of cometary ices. If the Fireball had not entered at such a grazing angle, it would have lost all its velocity in the upper atmosphere, possibly ending in an airburst, and any remnant would have fallen at terminal velocity.

The Great Daylight 1972 Fireball

IAU Definition of a Planet

In 2006, the International Astronomical Union (IAU) defined a planet as a celestial body that:

Is in orbit around the Sun,

has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

Has cleared the neighborhood* around its orbit.

*Clearing the neighborhood means that there are no objects of comparable size in its own orbital zone that are not under its gravitational influence.